1. Field of the Invention
This invention relates to a closure device made of plastic, which can be applied over a location, which can be punctured, of a closed container.
2. Discussion of Related Art
Various containers, particularly for storing flowable media, are available in commerce, wherein prior to opening them it is necessary to pierce a foil, or membrane, or even the container wall itself before the liquid medium can be removed from the container. For example, such containers are called soft cartons made of single-layer or multi-layered foil or coated cardboard, on which a closure device is glued or welded, wherein the closure device comprises a screw cap. Closure devices for such cartons have a lower element with a cylindrical pouring spout with an outer thread and a lower flange on the edge for fastening on the soft carton. Before the contents can be taken out of the soft carton it is necessary to unscrew the screw cap from the lower element and to puncture the container wall in the area of the pouring spout. The closure device has an integrated piercing element for puncturing the container wall in the area of the container opening.
Two systems in particular are known. With one system the screw cap is removed in a first step, and in the second step the piercing element is moved downward by the user for puncturing the container wall. Typical representatives of this version are known, for example, from European Patent Reference EP-A-0 543 119 and U.S. Pat. No. 5,297,696. So that the piercing element of such a closure device can be reasonably operated, the cylindrical pouring spout must have a lateral recess, which extends in the axial direction and approximately corresponds to the width of a finger. This known version is relatively simple in construction, however, it has one disadvantage that the pouring properties of such a closure are poor and there is a great danger that while actuating the piercing element the finger contacts the liquid contents. This leads to soiling of the finger and to the contamination of the liquid contents. This is particularly disadvantageous, because the containers are especially used for beverages, whose ability to keep is considerably reduced by contamination.
In a second version, there is an interactive effect between the screw cap and the piercing element. In the most frequent cases, the piercing element is pushed down through the container wall with the help of the screw cap. For this purpose, the screw closure is in an upwardly displaced position relative to the lower element prior to first opening, which in most cases is bridged by a security strip. Accordingly it is necessary to first remove the security strip, whereafter the closure is screwed down completely during which the screw cap, as well as the piercing element seated in the pouring spout are moved downward. Therefore the soft carton is punctured and opened during complete closure by the screw cap. In a third step it is necessary to completely unscrew the screw cap before the contents are freely accessible and can be poured out. A typical representative of this closure version is known from PCT International Publication WO 96/11850, for example. A closure device in accordance with PCT International Publication WO 99/64315 operates in a similar manner. With this device the piercing element has two sections of thread in different directions of lead. In a first screwing movement the piercing element is pushed through the container wall, and then the screw cap is unscrewed from the piercing element in the opposite turning direction.
While closures of this type are relatively new in connection with soft cartons, such closure devices are already known in various embodiments in an analogous construction for containers in the form of bottles, having container neck sealed by a membrane or foil. Closure devices of this type have not been successful in commerce. Besides frequently occurring sealing problems, one main problem is that the opening process does not agree with the habits of the consumer. It is therefore necessary to display elaborate instructions of how to open the carton. This is not only undesirable, but experience has shown that these instructions are hardly observed and that the consumer reads these instructions only after he already has destroyed the closure or rendered it ineffective.
On the basis of this knowledge, PCT International Publication WO 99/42375 proposes a device in which a piercing element cooperates interactively with a screw cap so that, in the course of simple unscrewing the screw cap, the piercing element is simultaneously moved so that it is conveyed downward and punctures the carton wall. This closure device is absolutely simple to operate and is comfortable for the consumer. However, in connection with this closure device the piercing element must be applied so it adheres to the carton wall, which is problematic. The punctured portion of the carton wall is caught on the piercing element. The edges of the carton wall remaining on the piercing element remain fixedly connected with it, even after first opening. The piercing element itself remains in the screw cap and is taken out when the screw cap is opened. Because paper or cardboard is a part of most soft cartons, the destroyed container wall, which is fixedly glued to the piercing element, again and again contacts the contents of the container and is conveyed outward again at each opening and can be repeatedly contaminated in the process, and residue from the liquid adhering to it can also be contaminated or oxidize, and thereafter again contact the contents when the screw cap is closed. Besides these undesirable use properties, this closure device has one disadvantage that it is extremely complex and expensive to mount. The reason for this is that the lower element and the piercing elements, must be glued or welded to the container wall. While the flange of the lower element can be welded on, depending on the carton material, the piercing element must be glued on in every case. If insufficient adhesive is applied, the piercing element is torn off the carton wall during opening without the carton necessarily being opened. If too much adhesive is used, adhesive connections between the piercing element and the lower element are formed and the screw cap can hardly be screwed on without the threads being stripped in the process.
A closure device is known from European Patent Reference EP-A-0 328 652. It is simple to operate, because when unscrewing the screw cap for the first time the piercing element is moved linearly downward and thus the membrane or the container wall is punctured.
Soft cartons necessarily must have a pre-punched predetermined opening spot. Such a predetermined opening spot is achieved by an impression stamping, by which the foil or the foil connection is only partially punched without achieving penetration, so that the piercing element makes possible the complete puncturing with little force. This is an extremely tricky punching operation, and thus the partial punching is relatively often too ineffective, so that required force the piercing element must generate is very large.
With the known closure device taught by European Patent Reference EP-A-0 328 652, the axially acting force is exerted on the piercing element by the screw cap, and the screw thread of the screw cap must be able to absorb this force. Accordingly, the screw thread on the cylindrical lower element and on the inner surface of the jacket wall of the screw cap must be made strong, with a large lead.
However, this is undesirable because a screw thread as a whole requires a more solid construction with increased wall thickness, which results in an additional weight of one to three grams even with relatively small closure devices. As the number of pieces required here is more than 109 pieces/year, a savings of material in the amount of more than 1000 tons of plastic material results, if a reduced lead can be realized.
With the solutions known today, and in particular also with the solution in accordance with PCT International Publication WO 99/62776, or the above mentioned European Patent Reference EP-A-0 328 652, the entire translatorial movement of the piercing element can be practically distributed only to a rotatory movement over 180° of the screw cap. Accordingly, the required force for the first actuation of the screw cap is large and depends greatly on the toughness of the material the piercing element has to puncture.